Distributed feedback 3.27 µm diode lasers with continuous‐wave output power above 15 mW at room temperature

GaSb‐based type‐I quantum well laterally coupled distributed feedback diode lasers emitting in the methane absorption band near 3.27 µm were designed and fabricated. The first‐order index grating with a period of 480 nm was defined by e‐beam lithography and etched on both sides of 6 µm‐wide shallow ridge waveguide. Coated 2 mm‐long devices demonstrated stable continuous‐wave single‐frequency operation in a wide temperature range with an output power of 15 mW at +17°C and 40 mW at −20°C. The Bragg wavelength temperature tuning rate was ∼0.27 nm/K.